A measurement circuit measures a waveform of electrical energy generated by a generator. The measurement circuit includes a sensor configured to sense a waveform having a first range of amplitudes, first and second circuits configured to filter the sensed waveform. Each circuit includes an attenuator configured to amplify an amplitude of the waveform by multiplying the waveform by an attenuation factor, an analog-to-digital converter (ADC) configured to digitally sample the amplified waveform, which has a second range of amplitudes, to obtain digital samples, a gain element configured to multiply the digital samples by a gain factor, and a factor adjustor configured to adjust the attenuation factor and the gain factor. The measurement circuit further includes a controller configured to calculate voltage and current of the waveform based on the digital samples and to control the generator based on the calculated voltage and current. The first range includes and is larger than the second range.